Buildings, large and small, must span space and resist axial and lateral forces, for example, forces caused by gravity, snow, wind or earthquakes. In residential construction this is most often accomplished by a series of triangular trusses in the attic space and wall and roof sheathing. Flat roofed and multi-story commercial buildings typically carry loads with walls or columns, and span spaces with combinations of girders, beams, and joists which are often trusses. Lateral bracing is accomplished with combinations of three bracing methods: a moment-resisting frame, diaphragm shear walls and floors or diagonal bracing. Moment-resisting frames are achieved through theoretically rigid joints, such as a welded steel connection or a continuously poured concrete intersection of column and beam. Diaphragm bracing (or shear walls) are able to rigidly resist forces in any direction. Diagonal bracing can take the form of knee braces (at frame corners) or floor-to-floor cross bracing.
The commercial construction industry is currently dominated by steel and concrete structural systems which are structurally functional but demand high inputs of energy and non-renewing natural resources. Wood is a much more environmentally friendly construction material due to its lower energy requirements, low emissions and renewable nature. However, dimensional wood framing cannot meet many commercial fire code requirements, and create the moment-resisting frame bracing possible in steel and concrete structures.
This leaves diagonal bracing as the bracing method available for timber construction. Dimensional wood framing typically employs plywood shear panels to provide lateral bracing. Heavy timber structures typically employ knee bracing—additional diagonal members attached to form triangles at each connecting corner of the column and beam frame. This system is functional but cumbersome—each knee brace requires additional member preparations and the fabrication of additional connections.
What is needed is a branched timber system for heavy timber construction that provides integrated lateral bracing and spanning in a post and beam structural system suitable for large buildings, with simplified construction and reduced cost.